18V vs 20V: The Truth Behind the Voltage — It’s All Marketing

If you’ve ever shopped for cordless tools, you’ve probably noticed something strange: some brands advertise 18-volt tools, while others proudly sell 20-volt tools. At first glance, 20V sounds more powerful — after all, twenty is bigger than eighteen! But here’s the truth: they’re the same thing. The difference is mostly marketing, not performance.

The Real Science Behind the Numbers

All lithium-ion batteries are made up of individual cells, and each cell has a nominal voltage of about 3.6 volts. When you connect five cells in series (standard for most cordless tools), you get:

5 cells × 3.6V = 18V nominal

However, when the battery is fully charged, each cell actually reaches 4.0 volts, giving:

5 cells × 4.0V = 20V max

So both 18V and 20V batteries use the exact same cells — the only difference is how the brand chooses to label them:

• 18V = the nominal (average operating) voltage
• 20V = the maximum voltage right after a full charge

Once you start using the tool, the voltage quickly drops to around 18V — no matter what’s printed on the label.

Why Do Brands Use Different Numbers?

It comes down to marketing strategy. Some brands (like DeWalt or Black+Decker) advertise the maximum voltage to make their tools sound more powerful. Others (like Makita, Bosch, or Milwaukee) prefer the nominal voltage, which is more technically accurate.

Both tools deliver the same performance, and their batteries are often cross-compatible when using the right adapter.

What Really Matters When Choosing Tools

Instead of focusing on the number printed on the battery, pay attention to:

• Amp-hours (Ah): determines how long the tool will run
• Build quality and features: brushless motors, torque settings, speed control, etc.
• Battery platform compatibility: staying within one ecosystem makes it easier to share batteries between tools

Whether you buy an 18V or 20V tool, you’re getting the same level of power — it’s just a different sticker on the battery.

The Bottom Line

Don’t let the voltage label fool you. 18V and 20V tools are identical in real-world use. The difference comes down to how the manufacturer markets their tools, not how they perform.

So next time someone brags about their “20V max” drill — you’ll know the truth: it’s really an 18V tool in disguise.